Yes, you can't read comic books or PDF files on an Eink device. I know that. I own one.
This is annoying for sure.
On the other hand, I personally don't want a mini computer when I just want to read a book. And I don't want to charge my handheld each night, that's something that I really hate.. But If I need a tablet for PDF files, then I'll obviously need to get one one day. Maybe a PDF facsimile is in fact a much better book than an Epub or Mobi file. I don't know yet.